New Methods Geared To Keeping Aircraft Safer On Ground

With visibility down to 1,800 ft. due to fog, see-and-avoid tactics are of no use in checking for traffic as we prepare to cross Runway 36C from taxiway Papa at the Memphis (Tenn.) International Airport. A loud call-out annunciation blares out, alerting us to stop on the taxiway just as the landing traffic, a regional jet, zooms by.

Though the encounter was virtual, the visual of the high-speed near-miss was realistic enough to make the aural warning and associated safety information on an electronic flight bag all the more relevant.

That simulator, mounted in a bay with two other full-motion simulators at the NASA Langley Research Center, is ground zero for testing a new batch of algorithms and technologies meant to keep aircraft safer on the ground by providing pilots with real-time access to traffic alerts via automatic dependent surveillance-broadcast technology.

The research is part of a much broader government and industry effort to reduce the potential for runway incursions, a problem that, despite FAA actions, continues to grow. Incursions, defined internationally as “any occurrence” involving the incorrect presence of an aircraft, vehicle or person on a takeoff or landing runway, are recorded in four categories at towered airports.

“The number of Category A and B incursions (the most severe) decreased after FAA implemented initiatives from its August 2007 Call to Action Plan for Runway Safety,” stated the Transportation Department's Office of Inspector General (OIG) in May when announcing an audit of the FAA's progress in runway safety efforts. “However, this trend is reversing.” The watchdog notes that reported serious runway incursions increased from fiscal 2010 to fiscal 2012, tripling to 18 from 6, and the total number of all runway incursions increased 21% between fiscal 2011 and 2012, to 1,150 from 954. “More concerning is that this increase occurred during a period when total air traffic operations declined slightly,” the OIG states. A second OIG runway safety audit has been underway since October, analyzing the FAA's efforts to address an NTSB recommendation issued in 2000 to provide incursion alerts directly to pilots.

The longest running of the NTSB's Most Wanted Safety Improvements, a direct incursion notification to pilots is an open sore between the two agencies. The NTSB wants the alerts available to pilots at all airports with commercial airline service, alerts it believes would be best provided by automatic dependent surveillance-broadcast “in” (ADS-B “in”) avionics, a feature the FAA did not mandate as part of its 2010 final rulemaking requiring ADS-B “out” avionics by 2020. ADS-B “in” brings GPS-based aircraft position and identification information for all transponder or ADS-B-equipped aircraft or vehicles into the aircraft's avionics for use in surveillance applications, including surface indicating and alerting.

FAA interventions underway that partially meet the NTSB's intent include runway status lights, a system the agency plans to put in place at 23 airports by 2016. The status lights use fused surveillance data to create “red lights” embedded in the pavement of certain runway entrance and threshold locations to alert pilots or vehicle operators that a runway is or will be occupied. A related concept the FAA is testing is called final approach runway occupancy signal (Faros). The system uses the airport surveillance data to flash the precision approach path indicators to warn landing pilots that a runway is occupied. The NTSB, however, says Faros “appears years from deployment.” Both technologies are typically only available at large airports.

The FAA in late July launched a market survey to evaluate “existing technologies which may be applied, or enhanced through additional research” to prevent runway incursions, with the focus on small- or medium-sized airports without traditional surface surveillance systems including radar and multi-lateration.

Though not mandated, work continues on ADS-B “in” applications. In 2009, the FAA funded surface indicating and alerting aircraft testing by avionics companies Honeywell and ACSS in the Seattle and Philadelphia areas, respectively, in 2009. The tests were successful from an algorithm standpoint, but both revealed unexpected ADS-B signal dropouts due to ADS-B signal disruptions caused by terrain and buildings between the two test aircraft, an issue the FAA continues to investigate but expects to solve. The pilot programs also fed information to an RTCA special committee that in 2010 published a safety, performance and interoperability requirements document for surface indicating and alerting (SURF-IA), a precursor for building FAA-approved SURF-IA equipment. The document identifies alerts that should be issued for aircraft and vehicles in the airport maneuvering area as well as within 3 nm of the runway threshold and 1,000 ft. above the airport elevation.

That document is the basis in part for the runway safety portion of NASA's NextSafe 3 project, part of the agency's Integrated Intelligent Flight Deck Technologies program. Earlier projects (NextSafe 2) focused on ADS-B and enhanced vision systems for delegated separation between aircraft and initial concepts for 4-D (position and time) surface operations (NextSafe 1).

“Our objective is to develop data and technologies which increase a pilot's or crew's ability to avoid, detect and recover from adverse events that could otherwise result in incidents or accidents, says NASA Langley's lead aerospace engineer, Randy Bailey, of the NextSafe program. “Our focus is on the terminal maneuvering area operations and emerging [next-generation air transportation system] issues.”

In the simulator, NASA engineers are testing three different aspects of runway safety during two-day simulator sessions with 12 airline pilot volunteers. Bailey is continuing earlier tests of a head-worn display with head tracker for presenting alerts, and aerospace engineer Denise Jones is testing conflict detection and alert scenarios as well as safety aspects of trajectory-based operations on the tarmac. The airline pilots spend one day participating in Jones's simulations and one day with the head-mounted displays.

The full-motion simulator is set up to emulate a generic large twin-engine transport, with cockpit display of traffic information (CDTI) presented on airport moving maps on two electronic flight bags outboard of each pilot. The cockpit is equipped with tracking devices to follow the pilots' eyes and head. Surveillance information is modeled as ADS-B, with no multi-path errors included, and air traffic control commands are automated and audible. Jones uses seven scenarios for the simulation, though pilots are not able to predict the particulars of a scenario. “The idea is to determine which methods are safest and which are acceptable for conflict prevention,” she says.

In the scenario with the near-miss with a regional jet, the pilot taxiing toward the runway first sees its outline on the CDTI light up in blue as the traffic closes in on the runway, indicating a caution that requires no action other than increased vigilance. An alert, however, requires immediate action. Having the CDTI was key to situational awareness as the outside visibility was simulated to be 1,800 ft. Data associated with a caution include arrows showing the horizontal/vertical movement of traffic, the aircraft identification, ground speed and distance. If the taxiing aircraft were to continue onto the runway in front of the arriving regional jet, the runway outline turns red and two “Warning, Traffic!” call-outs are sounded.

Jones also demonstrated a scenario in which we departed Runway 18C as another aircraft taxied across our runway beyond visual range. As the simulated jet accelerated, a red alert flashed on the CDTI with the accompanying call-out, causing Jones to reject the takeoff with ample room to spare. Per the RTCA document, the algorithm currently inhibits alerts above 80 kt. on takeoff.

Jones expects the simulation effort to be completed by the end of this month.